The present invention relates to containers for the food and beverage industry, and particularly to those beverage containers or cans which have lift-tab assemblies.
In the production of lift-tab can ends, the lift-tab is formed rough-side-up or bottom-side-up and it has been necessary to invert the tabs so that they are positioned smooth-side-up, prior to the attachment to a can end. This inversion has generally been accomplished manually, and consequently, it is desirable to provide a method wherein the tab is inverted automatically, thereby saving labor. Alternatively, it is desirable to provide a method of production wherein the lift-tab is formed rough-side-down or top-side-up, thereby eliminating the need for inversion of the lift-tab altogether.
In my invention, I provide a first press machine which makes the can end and a second press machine, or tab press, which makes the can end lift-tab. A third press machine, or conversion press, is provided which attaches the lift-tab to the can end to form lift-tab can ends. All three of the press machines are separate machines. Can ends are generally advanced from the first press to the third press by means of a conveyor.
Unlike many of the devices of the prior art, my invention does not provide a tab punch disposed at the exit of the tab press to remove the tab from the strip of material from which it is made, but rather accomplishes this task later in the lift-tab attachment process. By deferring the punching of the lift-tabs from the strip at the tab press exit, the strip as a whole may be inverted rather than necessitating the inversion of each individual lift-tab. To accomplish the inversion of the metal strip, a drive roller is provided on the frame of the tab press that rolls the strip of metal stock material, with the formed lift-tabs loosely attached, across a series of rollers or through a guide which inverts the metal strip via either a half twist or a half loop rotation in the guide or on the rollers.
Alternatively, a tab press including a die which presses tabs rough-side-down or top-side-up may be utilized. When such a tab press is utilized, it is no longer necessary to invert the lift-tabs by way of a half loop or half twist prior to their introduction into a conversion press.
With the lift-tabs now properly situated relative to the can ends through either (1) inversion of the tab by half loop or a half twist, or (2) use of a tab press, including a die which presses tabs rough-side-down or top-side-up, the invention provides two alternative methods of placing the lift-tabs into the proper position for attachment to the can ends.
In addition, the invention describes alternative methods of routing the lift-tabs through the process. The first method involves the running of the strip of metal stock material with the formed lift-tabs loosely attached through a locating means so that the strip will go into the conversion press with the lift-tabs being properly positioned with respect to a can end such that the conversion press may, in the same motion, detach the tab from the strip and attach the tab to the can end to form a lift-tab can end.
The second method of getting the tabs into working relationship with the can ends is to pass a strip of metal stock material with lift-tabs formed therein through a tab punching station where a tab punch knocks the formed tabs from the strip of metal stock material into a number of lanes with the smooth side of the tabs facing up. The lift-tabs then slide or are conveyed from the punching station to a conversion press. As the production of the lift-tabs is commonly quicker than the attachment of the lift-tabs to the can ends, and the lift-tabs will accumulate in their lanes adjacent to the conversion press.
The conversion press has attached thereto a tab ejector which feeds one lift-tab from the lane of tabs into the conversion press and properly positions the tab with respect to the can end so that as the conversion press takes a downstroke, the lift-tab is attached to the can end.
This invention provides for the use of any number of commercially available conversion presses. Additionally, the tab press is capable of operating such that a plurality of lift-tabs are created along a width of the strip of metal stock material. Furthermore, it is possible for the tab press to be operated with several lift-tab forming heads operating on a plurality of strips of metal stock material running alongside of one another in the tab press.
In the case where a single strip of metal stock material is pressed so that there are multiple tabs formed across its width, to avoid having to punch the tabs out of the strip prior to entering a conversion press or having to route the strip to a number of different conversion presses, the user can insert a commercially available plasma cutter or another conventional cutter which will precisely cut the wide strip of formed lift-tabs into individual strips of lift-tabs enabling the individual strips to be conveyed to and pass through a conversion press in the manner described above.
Another version of the second method of producing separate strips with one lane of formed lift-tabs in each strip is to provide a tab press with tooling which separates the single strip of metal stock material into individual strips and forms lift-tabs in each individual strip.
An alternative scheme involving the routing of separate tab-formed strips to their designated conversion presses is to pass a plurality of individual strips of stock material through the tab press in such a manner that the tab press produces separate strips with one lane of formed lift-tabs in each strip. This method of operation provides that if one or more of the conversion presses becomes inoperative, then the tab strip intended for use with that conversion press can be taken out of the inoperative press or presses and all other presses can continue to run. Separate paths through the press as well as separate guide means which route the strips along the separate paths would be necessary when utilizing the separate and individual tab formed strips. Each strip of stock material can be propelled through the tab press by a commercially available feeder such as a Ferguson Camtrol roll feed. A second roll or drive feed can be inserted to advance the tab formed strips on to the designated conversion presses.
Presses for converting ends for cans and the like are known. Presses of this type are available from the Minister Machine Company of Minister, Ohio. U.S. Pat. No. 4,568,230 shows a layout of a press for processing workpieces into finished can ends with an opening tab attached thereto.
Presses used for the manufacture of easy-open can ends generally comprise a press bed mounted on legs which rest on the floor. Four columns or uprights are mounted on the press bed. The columns or uprights support a crown in which a main drive for the press components is mounted. The columns have slides attached therein for supporting a reciprocating main ram. The main ram carries the upper tooling of the main die set, which cooperates with lower tooling on the bed. The main die set defines a plurality of stations in which the can ends are progressively converted into easy-open can ends. A conveyor carries the can ends into and through the stations of the die set. The tabs are formed by tab tooling, which is supplied with strip stock by a stock feed device. The tab tooling forms a tab and separates it from the strip stock for attachment to a can end.
The tab tooling has conventionally been mounted on the press bed laterally of the conveyor and laterally of the main die. The tab tooling may also be split so that it is arranged laterally on both sides of the main die. A bridge is required to transfer the tab stock strip across the main die set. Such an arrangement is shown in U.S. Pat. No. 4,568,230. The upper tooling is mounted on the main ram of the press.
One of the deficiencies associated with this arrangement of the tooling is that it is difficult to access the tooling for maintenance. Access to the can end tooling is difficult due to the presence of the tab tooling on one side of the main die and the tab tooling and tab stock feed device on the other side of the main die. The lateral placement of the tab tooling also increases the depth of the press from front to back. This requires a larger bed which increases the weight of the press and reduces its speed.
The present invention overcomes the disadvantages of the laterally-placed, split tab tooling by locating the tab tooling in another press where the only tooling is the tooling associated with the tab press. Placing the tab die set in another press allows full access to the main die from either the front or back of the press. Neither the tab tooling or its stock feed device obstruct access to the main die set. This placement of the tab tooling also permits a reduction in the width of the press between the columns and thus a reduction in weight of the press which allows the press to run at a higher speed. Another benefit of the tab tooling placement of the present invention is that it allows servicing of the tab die within the press. Still another benefit of placing the tab tooling and the can end tooling in separate presses is that there can be an additional tab press ready for substitution into the production line at any time a tab press in operation breaks down or needs to be shut down for repairs. The advantage of the present invention is increased productivity through higher operating speed and reduced down time for maintenance and tab press stock-up.
This invention resides in a process and system for use when forming lift-tab can end assemblies, wherein each lift-tab can end assembly includes a lift-tab having a smooth side, an opposite roughened side, a hole extending between the sides of the lift-tab, and a rivet or shaft, extending from the can end, adapted to receive the hole in the lift-tab, during an assembly-forming process.
One embodiment of the process includes a step of conveying a strip of metal stock material containing lift-tab forms from the tab press to a conversion press, during which conveyance the metal strip is inverted by passage along or through a half-loop of about 180 vertical degrees, or a half-twist of about 180 degrees, so that the strip of metal stock material is inverted from the orientation it had when it emerged from the tab press. The inverted strip of metal stock material is then conveyed into the conversion press, where each tab is separated from the strip of metal stock and attached to the can end in the same motion of the conversion press.
The length of the run between the tab press and the conversion press will determine whether any guide means are required to support the strip of metal stock.
The system of the invention includes means for advancing formed can ends through a first workstation so that as the can ends are advanced therethrough, the shafts or rivets formed therein protrude generally upward. Means are also included for conveying a strip of metal stock through a tab press wherein a first press means is provided for stamping lift-tab forms into the strip of metal stock so that the lift-tabs are loosely attached to the remainder of the strip and are oriented smooth-side-down as they exit the tab press. The conveying means is adapted to direct the strip stock which has been stamped with the lift-tab forms along a path through which the strip stock is inverted, so that as each lift-tab moves into the conversion press, the lift-tab is positioned smooth-side-up.
In an alternative embodiment, the step of inverting the lift-tabs by about 180xc2x0 is eliminated through the use of a tab press having a die arranged such that the lift-tabs are punched rough-side-down or top-side-up.
The system also includes means for directing the lift-tab formed strip to a position such that a lift-tab is disposed above a can end positioned in the conversion press. The directing means is coordinated with the can end conveying means so that as each can end is advanced into the attachment position at the conversion press, a lift-tab within the strip of metal is moved above the can end so that the hole in the lift-tab is positioned directly above the upwardly-directed shaft formed in the can end.